<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        var a = 0;
        if (a){
            alert("0为真")
        }else{
            alert("0为假")
        }
        var b = 0;
        if (b){
            alert("b为真")
        }else{
            alert("b为假")
        }

        var c = true;
        var d = false;
        var e = null;

        alert(c&&d);
        alert(e&&d);
        alert(c&&e);

        alert(c||d);
        alert(c||e);
        alert(e||d);

    </script>
</head>
<body>

</body>
</html>